Extended reach mechanism for a truck

ABSTRACT

An extended reach mechanism for a lift truck in which a generally vertically positioned post is pivotally connected at its lower end to the rear end of the truck, and a boom connected to the upper end of the post extends forwardly therefrom and has an attachment at the forward end for raising and lowering a load. A first power means pivots the post forwardly and rearwardly to advance and retract the boom, and a second power means spaced forwardly from the post raises and lowers the forward end of the boom. In order to maintain the boom and the load on the attachment on a plane as the boom is advanced and retracted, an electrical system is incorporated in the mechanism which is responsive to the movement of the post for adjusting the second power means as the load is advanced and retracted. The first and second power means are preferably hydraulic cylinders controlled by a hydraulic system having a manually controlled valve for each cylinder and an electrically controlled valve for the second power cylinder responsive to a rheostat operated by the pivotal movement of the post.

United States Patent [191 Frank Oct. 22, 1974 EXTENDED REACH MECHANISMFOR A TRUCK [75] Inventor: Gary D. Frank, Battle Creek, Mich.

[73] Assignee: Clark Equipment Company,

Buchanan, Mich.

[22] Filed: July 7, 1972 [21] Appl. No.: 269,855

[52] U.S. C1 214/762, 214/763, 214/770 [51] lint. Cl E02f 3/86 [58]Field Of Search 214/763, 762, 764, 770, 214/730 [56] References CitedUNlTED STATES PATENTS 3,070,244 12/1962 Lull 214/770 3,410,433 11/1968Brown 214/763 3,463,335 8/1969 Brownell i 214/762 3,698,580 10/1972Carlson 214/1 CM 3,713,557 1/1973 Seaberg 214/763 3,726,423 4/1973 Lark214/764 Primary ExaminerRobert J. Spar Assistant Examiner-John MannixAttorney, Agent, or FirmHobbs & Green [5 7 ABSTRACT An extended reachmechanism for a lift truck in which a generally vertically positionedpost is pivotally connected at its lower end to the rear end of thetruck, and a boom connected to the upper end of the post extendsforwardly therefrom and has an attachment at the forward end for raisingand lowering a load. A first power means pivots the post forwardly andrearwardly to advance and retract the boom, and a second power meansspaced forwardly from the: post raises and lowers the forward end of theboom. in order to maintain the boom and the load on the attachment on aplane as the boom is advanced and retracted, an electrical system isincorporated in the mechanism which is responsive to the movement of thepost for adjusting the second power means as the load is advanced and retracted. The first and second power means are preferably hydrauliccylinders controlled by a hydraulic system having a manually controlledvalve for each cylinder and an electrically controlled valve for thesecond power cylinder responsive to a rheostat operated by the pivotalmovement of the post.

10 Claims, 5 Drawing Figures BAIENIEnmzzzsu smaur FIG. 3

FIG. 4

i: m 5mm MW L; MWEGU I F D55 M, 4 w

EXTENDED REACH MECHANISM FOR A TRUCK An extended reach mechanism for atruck has special applications and advantages in the construction fieldin that loads can be picked up, delivered to the construction orbuilding site, and lifted to and placed on scaffolding, without thenecessity of special or separate handling to transfer the load from thetruck load carrying attachment to the scaffold platform or other worksupporting structure. This type of truck has the further specialadvantage of being able to pick up a load immediately in front of thetruck where the ground is firm, transport the load to the work site, anddeliver it to the scaffolding platform or partially completed buildingand yet avoid driving onto the usually soft backfill around the outsideof the building. The extended reach trucks of the standard or well knownconstruction utilize a parallelogram arrangement for the memberssupporting the forwardly extending support or boom, with the memberspivotally connected to one another and to the truck frame. Movement ofthe members forwardly to a point approaching the fully extended positionresults in a drooping of the forward end of the boom, thus causingdifficulty in picking up a load and positioning it at the desired leveland maintaining it at that level while advancing the load until it isdeposited onto the scaffold platform or other work support. Further, theproblem caused by the failure of the prior extended reach trucks toadvance the load on a horizontal plane, particularly as the loadapproached its fully extended position, was compounded by the effect ofheavy loads compressing the tires on the front wheels adjacent the loadattachment and by thedip caused by soft ground traversed by those wheelsas the truck approached the place where the load was to be discharged.While movement of the load ona horizontal plane would not eliminate thedifficulty caused by the load on the tires or soft ground, it wouldresult in easier and more effective control of the extended reachmechanism and load attachment under those adverse conditions. It istherefore one of the principal objects of the present invention toprovide an extended reach truck in which the load supporting mechanismwill operate automatically to maintain the load on the fork or bucketona plane as it is moved forwardly or rearwardly between its maximum andminimum limits of reach, regardless of the tendency of the load to dipas a result of compressing the tires or soft ground, and which can beoperated by a single control means for advancing and retracting theload.

Another object of the invention is to provide a truck having an extendedreach mechanism which has the ability to pick up a load below groundlevel, and which can be controlled either manually or automatically tocompensate for compression of the truck tires by the load or downward orupward tilting of the forward end of the truck as a result of theterrain,'to obtain move ment of the load on the horizontal plane underthose conditions.

Still another object of the invention is to provide a material handlingtruck of the extensible reach type, in which the reach mechanism iscontrolled by an electrical and hydraulic system which will provideeffective control of the lift and reach mechanism and which will performefficiently under various adverse operating conditions.

A further object of the invention is to provide a mate rial handlingtruck having an extended load mechanism of the aforesaid type which isso constructed and designed that it has maximum stability in all loadhandling positions and can be adapted to various types of truck designswithout any appreciable modifications in the basic structure of themechanism.

Further objects and advantages of the present invention will becomeapparent from the following description and accompanying drawings,wherein:

FIG. 1 is a perspective view of an extended reach truck embodying thepresent invention showing the extended reach mechanism in both itslowered position in full lines and in its raised position in brokenlines;

FIG. 2 is a side elevational view of the presentlift truck illustratingthe extended reach mechanism in its lowered and elevated positions;

FIG. 3 is a frontelevational view of the truck shown in FIGS. 1 and 2;

FIG. 4 is a rear elevational view of the truck shown in the precedingfigures; and

FIG. 5 is a schematic diagram of the operating and control systems ofthe extended reach mechanism.

Referring more specifically to the drawings, numeral 10 indicatesgenerally a lift truck on which the extended reach mechanism 12 ismounted, the truck having from drive wheels 14 and 16 and rear steerablewheels 18 and 20. While only the front wheels are driven and the rearwheels are steerable, the truck may be one in which the front and rearwheels are steerable and in which both sets of wheels are drive wheels.The motor driving the truck and providing the power for operating theextended reach mechanism is under hood or cover 22 and is mounted onframe 24, and the truck is controlled by an operator from cab 26 whereinthe manual controls shown in FIG. 5 are located. While the extendedreach mechanism may be mounted on various types of trucks and truckframes, the one shown has two longitudinal side members anda pluralityof cross members forming the support for the motor, controls and cab,and also forming the basic support for the extended reach mechanism.Various changes in the truck structure can be made to adapt it to thedesired operation to be performed thereby.

The extended lift mechanism. 12 includes a pair of posts 30 and 32normally assuming a substantially upright position and being pivotallymounted on a shaft 34 secured to the rear end of frame 24 by mountingfixture 36. The two posts are rigidly joined to one another by a steelplate 38 to form a bifurcated structure which is adapted to tiltforwardly and rearwardly on the two pivot means 40 and 42, respectively,at opposite ends of shaft 34. Boom or arm 44 consisting of twolongitudinal members 45 and 46 is pivotally connected to the upper endsof posts 30 and 32, respectively, and ex tends forwardly therefromgenerally parallel laterally to the two sides of frame 24, the twomembers being adapted to pivot on the upper ends of the posts from aposition such as that shown in solid lines in FIG. 2 to an elevatedposition shown in broken lines. Longitudinal boom arms 45 and 46 arepivotally connected to the upper end of posts 30 and 32 by shafts 48 and50, respectively. A plurality of cross members 52 tie the twolongitudinal arms together so that they operate in unison in movingloads from one position to another, both forwardly and rearwardly and upand down. Joined to the forward end of the arms and forming a partthereof are extensions 54 and 56 joined rigidly at one end to the mainportion of the arms and pivotally supporting an upright 60 at the otherend. Pivot pins 62 and 64 Y connect the forward end of the extensions tofixtures 66 and 68, respectively, on the upright. The upright, which maybe considered conventional for the purpose of the present descriptionand which is shown here fragmentarily to assist in fully understandingthe invention, supports a fork lift attachment 70 mounted on the frontof upright 60 on vertically spaced tracks 72 and 74, and is moved tovarious vertical positions on the upright by a suitable power mechanismsuch as a hydraulic cylinder 76. The fork attachment is provided withtwo spaced tines 78 and 80 rigidly connected to and supported bycarriage 82.

Posts 30 and 32 are pivoted forwardly and rearwardly on pivots 40 and 42by cylinder assemblies on opposite sides of the truck which areconnected at one end to frame 24 by fixture 92 and connected at theother end through the piston rod 93 to pivot means 94, the two hydrauliccylinders being operated together from the same hydraulic system. Theboom is raised and lowered and pivoted relative to posts 30 and 32 by apair of hydraulic cylinder assemblies, one of which is shown at numeral100, the lower end of each cylinder being connected to the frame by afixture 102 on each side, and the other end through piston rod 103 tothe arms by a fixture 104 on each side, and the two cylinder assembliesbeing operated in unison from the same hydraulic system. The cylinders90 and and the interconnecting frame andarm form a trapezoidconfiguration which permits the mechanism easily to dip forwardly wellbelow ground level to pick up or deposit a load. It is seen that fixture104 for the upper end of cylinder assembly 100 is spaced further frompivot 48 than fixture 102 for the lower end of the assembly is frompivot means 40. The upright is moved to various angular positions ormaintained in a vertical position as the arms are raised and lowered bya pair of hydraulic cylinders, one of which is indicated by numeral andis pivotally connected to extension 54 by a fixture 112 and to one ofthe side members of the upright by a fixture 114. The hydraulic cylinder76 on the upright may be operated from the hydraulic system of the truckas part of the system which operates the hydraulic cylinders of theextended reach mechanism or by a separate hydraulic system, as desired.

The hydraulic system for operating cylinder assemblies 90 and 100 isshown schematically in FIG. 5, numeral indicating generally the portionof the system controlling cylinder 90, numeral 122 indicating generallythe system controlling cylinder 100, and numeral 123 indicatinggenerally a compensating system for leveling the boom to prevent droopor unintentional lift when the boom is moved forwardly and rearwardly,respectively. System 120 is connected to a hydraulic pump 124 whichdelivers oil from a tank or sump 126 through line 128 to valve 130. Thevalve is connected to cylinder 90 on opposite sides of piston 132 bylines 134 and 136, and line 128 is connected to the sump by line 138.When post 30 is to be moved forwardly, i.e., to the left as illustratedin FIG. 5, the valve 130 is moved to the left, thus connecting a supplyline 128 with line 136 and line 134 with return line 138, causing piston132 to move to the left and pivot post 30 forwardly. When the post is tobe moved in the opposite direction, the valve is moved to the right, asviewed in the drawing, thus connecting line 128 with line 134 and line136 with return line 138. After the post has been moved to the desiredposition, the valve is returned to its center position where thehydraulic fluid from the pump in line 128 is returned to the sumpthrough line 138. A pressure relief valve (not shown) may connect lines128 and 138 to limit the maximum pressure in line 128 for operating thepiston when the pump is in Opera tion.

Hydraulic system 122 is connected to pump 124 by line 128' which is abranch of line 128, and line 128 is connected to valve 158 forcontrolling cylinder 100. The valve is connected to cylinder 100 on theunder side of piston 160 by line 162 and to the cylinder above thepiston by line 164. The valve is also connected to sump 126 through line166. When boom 12 is to be raised, the valve is moved to the left, asviewed in FIG. 5, by connecting line 128 with line 162 beneath piston130, thus causing the piston and piston rod 103 to move upwardly,elevating the forward end of the boom and the upright and attachment.When the valve is in the position for raising the boom, line 164 isconnected through the valve to line 166 to sump 126. To lower the boom,the valve is moved to the right as viewed in FIG. 5, thereby connectingline 128' with line 164 and line 162 with return line 166 and sump 126,thus causing the piston 160 and rod 103 to move downwardly.

After the load has been moved to the desired height, the boom is oftenextended forwardly by the operation of cylinder assembly 90 moving posts30 and 32 forwardly. This movement will normally. raise or lower thefork attachment and upright, thus creating a problem for the operator inmaintaining the load at the desired height. In the present extendedreach lift truck, a mechanism is incorporated which compensates for thisotherwise change of level of the load as it is moved forwardly orretracted by the boom, the attachment and load being thus maintained ona horizontal plane during the foregoing movement. In the extension orretraction of the boom, the droop or rise, respectively, causes an errorin positioning of the load. The linkage 170 transmits the direction oferror to switch 172 which closes the corresponding circuit to aproportional valve 174. The valve is provided with two solenoids 176 and178, and lead connects the source of 'power such as a battery indicatedat numeral 182, to solenoid 176, and lead 184 connects solenoid 178 withthe source of power. The switch, operated by the movement of post 30 orthe operator, selects the position of switch 172, and hence the lead 180or 184 energizes the proper solenoid 176 or 178 for operating valve 174.The valve is supplied with hydraulic fluid under pressure by pump 186through line 188, and is connected to hydraulic cylinder 100 beneathpiston 160 by a hydraulic line 190. When the valve is in this operatingposition, valve 158 is in neutral, and line 164, which is connected tocylinder 100 above the piston, is connected to sump 126 through valve158 and line 166, thereby permitting effective operation of the cylinderby the fluid delivered through line 190 from valve 174.

Valve 174 is controlled during the operation by a potentiometer 200operated in response to the pivotal movement of post 30, as indicatedschematically by linkage 202. The greater the rise or drop of the loadas a result of the horizontal movement of the boom, the further thepotentiometer rotates, causing the corresponding current variationthrough switch 172 to operate valve 174 to raise or lower piston 160 andhydraulic cylinder 100 the degree necessary to make the correction formaintaining the movement of the load and boom on a horizontal plane.This maintains the load and boom at the level selected by the operatorprior to the horizontal movement thereof. If movement of the fork and/orload to a different elevation is required, valve 158 is actuated tocontrol cylinder 100.

Actuation of valve 158 closes a switch 204 and opens a clutch 206through leads 208 and 210 to open switch 172, and thereby renderspotentiometer 200 and system 123 inoperable. Centering of valve 158opens switch 204 and engages clutch 206, thereby again placing theleveling system in operation.

In the operation of an extended reach truck having the lift mechanismdescribed herein, starting with the fork attachment in its loweredposition, the operator moves the truck forwardly to slip the tines ofthe fork attachment under a load, and lifts the load from the ground,normally using the upright to perform the initial lifting operation andthe boom for the subsequent lifting operation. The truck is thenmaneuvered to the position where the load is to be discharged, such as,for example, on the platform of a scaffold, and cylinders 100 areoperated to raise boom 44 and the load on the fork attachment to thelevel at which the load is to be discharged. This operation is performedthrough the operation of control valve 158. With the load in position ata level slightly above the platform, cylinder 90 is operated by theoperation of valve 130 to pivot posts 30 and 32 forwardly. As thisoperation is taking place, valve 174 of the compensating mechanism isoperated to operate cylinder 100 in the direction to raise the forwardend of boom 44 and maintain the load on its original elevated planethroughout the pivotal movement of the posts and the horizontal movementof the boom.

When the load is being advanced, switch 172 is connected with line 184to energize solenoid 178 of valve 174, thereby connecting line 188 frompump 186 with line 190, which is connected to cylinder 100 beneathpiston 160. The current for operating solenoid 178 is controlled bypotentiometer 200 which in turn is operated in response to the pivotalmovement of post 30 through linkage 102. While valve 174 is beingcontrolled by potentiometer 200, the amount of hydraulic fluid requiredto lift the boom to maintain the original plane of the load is deliveredthrough line 190 to cylinder 100. The operation of the compensatingsystem is rendered inoperable by switch 204 and clutch 206 when valve158 is operated to operate cylinder 100. If valve 158 is operated,switch 204 energizes the circuit for disengaging clutch 206 to preventthe operation of the compensating system while valve 158 is supplyingfluid to hydraulic cylinder 100.

When the boom is being retracted, switch 172 is connected to lead 180which energizes solenoid 176 to move the valve in the direction to drainthe hydraulic fluid from the lower end of cylinder 100 and return it tosump 126. This permits the piston to move downwardly and adjust the loadand boom properly for maintaining them in the desired constant elevatedplane. After switch 172 is closed, the potentiometer controls theoperation of solenoid 176 in the same manner as it controlled thesolenoid 178 as previously described.

One of the advantages of the electrical compensating system is that itcan be programmed to provide the desired depth or lift under variousoperating conditions. The programming can be changed as required fromone lift truck operating condition to another, and can be adjusted tomeet various operating conditions, such as firmness of the ground andthe weight of the load on the vehicle tires. This may be accomplished byadjusting the operation of potentiometer 200.

While only one embodiment of the present extended reach truck has beendescribed in detail herein, various changes and modifications may bemade without departing from the scope of the invention.

I claim:

1. An extended reach mechanism for a lift truck having a frame with aforward end and a rearward end, comprising a substantially vertical postpivotally connected at its lower end to the rearward end of the truckframe, a boom pivotally connected to the upper end of said post andextending toward the forward end of the truck frame, a load attachmentat the forward end of said boom, a first power means connected to saidpost for pivoting said post forwardly and rearwardly for extending andretracting said boom, a control means for said first power means, asecond power means spaced forwardly from said post and being extensibleand retractable for pivoting said boom upwardly and downwardly to raiseand lower a load on said attachment, a first control means forcontrolling said second power means, a second control means operatedelectrically for said second power means, and an electrical meansresponsive automatically to the pivoting movement of said post foractuating said second control means to extend or retract said secondpower means to maintain the forward and rearward movement of the forwardend said boom on a substantially constant horizontal plane for any givenelevation of said forward end.

2. An extended reach mechanism for a lift truck as defined in claim 1 inwhich said first and second mentioned, power means include hydrauliccylinders, a source of hydraulic fluid under pressure, and a pair ofvalves for controlling the operation of the cylinders.

3. An extended reach mechanism fora lift truck as defined in claim 2 inwhich said second control means consists of an electrically controlledvalve operated by said electrical means responsive to the movement ofsaid post.

4. An extended reach mechanism for a lift truck as defined in claim 1 inwhich a power means interconnects the boom and said attachment to movesaid attachment angularly with respect to said boom.

5. An extended reach mechanism for a lifttruck as defined in claim 1 inwhich said second control means is operated by a solenoid means, andsaid electrical means responsive to the movement of the post foractuating said second control means includes a potentiometer.

6. An extended reach mechanism for a lift truck as defined in claim 3 inwhich said second control means is operated by a solenoid means, andsaid electrical means responsive to the movement of the post foractuating said second control means includes a potentiometer.

7. An extended reach mechanism for a lift truck as defined in claim 5 inwhich said electrical means responsive to the movement of said post iscontrolled by a switch and a circuit for energizing said second controlmeans selectively to operate said second power means, either to advanceor retract said second power means cuit and a switch responsive to themovement of the first control means for rendering said second controlmeans inoperable 10. An extended reach mechanism for a lift truck asdefined in claim 5 in which said second means includes a circuit and aswitch responsive to the movement of the first control means and aclutch for rendering said potentiometer inoperable.

1. An extended reach mechanism for a lift truck having a frame with aforward end and a rearward end, comprising a substantially vertical postpivotally connected at its lower end to the rearward end of the truckframe, a boom pivotally connected to the upper end of said post andextending toward the forward end of the truCk frame, a load attachmentat the forward end of said boom, a first power means connected to saidpost for pivoting said post forwardly and rearwardly for extending andretracting said boom, a control means for said first power means, asecond power means spaced forwardly from said post and being extensibleand retractable for pivoting said boom upwardly and downwardly to raiseand lower a load on said attachment, a first control means forcontrolling said second power means, a second control means operatedelectrically for said second power means, and an electrical meansresponsive automatically to the pivoting movement of said post foractuating said second control means to extend or retract said secondpower means to maintain the forward and rearward movement of the forwardend said boom on a substantially constant horizontal plane for any givenelevation of said forward end.
 2. An extended reach mechanism for a lifttruck as defined in claim 1 in which said first and second mentionedpower means include hydraulic cylinders, a source of hydraulic fluidunder pressure, and a pair of valves for controlling the operation ofthe cylinders.
 3. An extended reach mechanism for a lift truck asdefined in claim 2 in which said second control means consists of anelectrically controlled valve operated by said electrical meansresponsive to the movement of said post.
 4. An extended reach mechanismfor a lift truck as defined in claim 1 in which a power meansinterconnects the boom and said attachment to move said attachmentangularly with respect to said boom.
 5. An extended reach mechanism fora lift truck as defined in claim 1 in which said second control means isoperated by a solenoid means, and said electrical means responsive tothe movement of the post for actuating said second control meansincludes a potentiometer.
 6. An extended reach mechanism for a lifttruck as defined in claim 3 in which said second control means isoperated by a solenoid means, and said electrical means responsive tothe movement of the post for actuating said second control meansincludes a potentiometer.
 7. An extended reach mechanism for a lifttruck as defined in claim 5 in which said electrical means responsive tothe movement of said post is controlled by a switch and a circuit forenergizing said second control means selectively to operate said secondpower means, either to advance or retract said second power means tomaintain the load and boom on a substantially constant plane as the boomis advanced or retracted by the pivoting of said post.
 8. An extendedreach mechanism for a lift truck as defined in claim 7 in which a meansis provided for rendering said second control means inoperable when saidfirst control means for controlling the second power means is inoperation.
 9. An extended reach mechanism for a lift truck as defined inclaim 7 in which said means includes a circuit and a switch responsiveto the movement of the first control means for rendering said secondcontrol means inoperable.
 10. An extended reach mechanism for a lifttruck as defined in claim 5 in which said second means includes acircuit and a switch responsive to the movement of the first controlmeans and a clutch for rendering said potentiometer inoperable.